Field
The present invention relates to a high pressure pump valve assembly, for use in high pressure applications such as hydraulic fracturing. In particular, the invention relates to the design and composition of intake and discharge valve assemblies.
Description of the Related Art
The use of high pressure pumps for a variety of different applications is well known in the industry. Some of the most common applications include industrial cleaning, water jet cutting, hydroforming, as well as a wide range of hydraulic applications. Because the components of these pumps are subject to high levels of pressure, they require continuous upkeep, which is both expensive and time consuming. One of the most popular applications of high pressure pumps is in hydraulic fracturing.
Given the ever increasing demand for affordable oil and natural gas, many alternatives to traditional oil drilling have developed over the years. One alternative, which has seen tremendous growth over the past decade, is hydraulic fracturing. Hydraulic fracturing is the process of drilling vertically into a targeted shell area, and then proceeding to drill horizontally across that shell. The shell formation is then fractured, generally with the use of explosives, and fracturing fluid, which is generally a mixture of water, sand or proppant, as well as other additives, is pumped into these fractures. The fracturing fluid helps to expand the initial fractures created in the shell. Once the fracturing fluid is pumped out of the wellbore, natural gas or oil begins to flow through the created cracks into the wellbore, at which point the gas or oil is extracted.
During drilling, a pressurized drilling solution, known as mud, composed of water and sand, is fed to the drill head in order to prevent the drill head from overheating and to provide proper lubrication. Another function of the mud is that it is used to help remove cuttings from the drilling wellbore. Throughout the drilling process, mud, cuttings, and the previously mentioned fracturing fluid are moved up and out of the wellbore. A high pressure hydraulic fracturing pump is used to control the discharge of these substances from the wellbore.
High pressure pumps utilize both intake and discharge valves. These valves are subjected to high pressures from both the pump itself and in certain applications fluid from a wellbore. This pressure causes the valves to have a very short life span, typically between 10 to 30 hours. As such, these valves have to frequently be replaced. Replacing these valves, however, is a cumbersome undertaking. One must first take apart the pump, in order to gain access to the valves, and then the entire valve assembly has to be removed and replaced with specialty tooling.
A typical valve assembly contains a seat and a valve. The function of the valve assembly is to allow the fluid to flow through it in one direction, and prevent the fluid from flowing through it in the opposite direction. The seat is traditionally a metal body that is pressed firmly into the fluid end housing to create a seal. Fluid enters through the first end of the seat, and then reaches the valve. Once a certain pressure differential is reached, the valve opens, a spring disposed above the valve compresses, and fluid moves past the valve. When the pressure on one side of the valve is equal to the pressure on the second side, the spring will start to close the valve. When the pressure on the top of the valve is greater than that on the bottom, the valve is pushed against the seat in order prevent the fluid from flowing in that direction. Due to the high pressures involved in this application, the valve generates high impact forces on the seat which causes both the seat and the valve to become warped and damaged within a short period of time.
The valve and the seat are deformed in such a way that they can no longer efficiently effectuate the desired flow of the fluid into and out of the pump. The high pressure causes the valve to be pushed against the seat, and in turn creates a high impact force which deforms the metal of the valve and of the seat. This causes the deformable seal of the valve to compress in such a way that is beyond its capabilities. This also has the effect of allowing the edge of the deformable seal to extend beyond the outer edge of the seat, which causes the deformable seal to crack. As the metal of the valve and seat wear down, the deformable seal is required to compress even further, which quickly escalates the rate of failure of the valve assembly. These effects are exacerbated by the fact that a grainy fluid is flowing through the intake and discharge valves and can become crushed and lodged between the surfaces.
As such, the valve and the seat need to be replaced at a high frequency. This replacement is a cumbersome, time-consuming, expensive process. The seat is pressed into the fluid end housing with sufficient force to prevent any fluid from leaking out of the pump, and to withstand high levels of pressure. Removing the seat, therefore, is a difficult undertaking. Although removing the valve is less difficult than removing the seat, many other components still need to be removed in order to get to the valve. Additionally, the seat is generally replaced every time the valve is replaced because of excessive wear on both components.
For the foregoing reasons, there is a need for a more durable valve assembly with an increased life span. Such a valve assembly needs to be better able to withstand the pressures and harshness of various applications, including hydraulic fracturing pumping.